The proposed research consists of 6 projects related to neural mechanisms controlling the respiratory act. Projects 1 and 2 explore the execution of inspiratory-expiratory (I-E) phase switching. The global characteristics are investigated by procedures which alter volume-feedback during the terminal phase of inspiration. Single unit recordings will be carried out to define central neuronal correlates of the response to these procedures. Project 3 investigates the basic neuronal mechanisms underlying respiratory rhythmicity in a primitive nervous system (Lamprey). The aim of project 4 is to identify specific neural mechanisms controlling the respiratory pattern during sleep in unmedicated cats studied before and after various neuronal lesions. Project 5 examines the respiratory cycle and other respiratory variables during sleep in normal humans and patients with lung disease. In Project 6 the pathogenesis of sleep apnea will be investigated. In particular, the factors contributing the upper airway obstruction during sleep will be sought. We will examine the possibility that pharyngeal obstruction results from hypotonia of the genioglossus muscle.